1. Field of Invention
The present invention relates to a method and apparatus for transporting Ethernet and radio frequency signals in a fiber-optic system.
2. Related Prior Art
In fiber-optic communication, to increase the utility rate of a fiber-optic and the convenience of exchange with a web, signals in different forms must be transmitted through the fiber-optic. Usually, this is done in one of the following ways:
A first solution is wavelength division multiplexing (“WDM”). WDM provides adequate differences between the wavelengths of the signals. Like frequency multiplexing, WDM prevents the interferences of signals in different forms at a same operative frequency (analog) or operative rate (digital). Thus, digital signals can be transmitted at a high bit rate.
A second solution is frequency division multiplexing (“FDM”). FDM uses different carries to separate signals in different forms. The bandwidth required for digital signals however increases as the bit rate increases. Hence, the differences between the frequencies of the signals must increase in order to avoid interferences, i.e., the amount of channels available in a fiber-optic decreases as the bit rate increases. Moreover, a M-ary phase-shift keying (“M-PSK”) or multi-level quadrature amplitude modulation (“M-QAM”) may be used to transform bits into symbols in order to generate a symbol rate of the digital signals so as to reduce the required bandwidth.
A third solution is light polarization quadrature multiplexing. The third solution uses a single wavelength to transmit two signals in different forms. To avoid the signals from interfering each other, the signals are carried on two quadrature polarizations of a single wavelength. Thus, a single wavelength can transmit two signals simultaneously.
However, the conventional solutions involve complicated fiber-optic communications, high costs or low bit rates of digital signals.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.